Back Forty: How to protect farmworkers from heat-related kidney disease

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By Nancy Averett

Farmworkers pick and pack melons in Firebaugh, California, on July 9, 2021, when temperatures hit 110 degrees. AP photo by Terry Chua.

Twenty years ago, Ramón García-Trabanino, a nephrologist in El Salvador, published a study that showed that nearly 70 percent of kidney failure cases in his hospital were occurring in healthy young men. Many of these patients were farmworkers, and they had neither diabetes nor hypertension, two common comorbidities for kidney disease. 

His observation sparked a tsunami of interest with researchers flocking to Latin America to study what has come to be known as “kidney disease of unknown cause,” or CKDu. Today, researchers still don’t know exactly what causes CKDu, but they believe it may be due to some combination of heat stress, dehydration, exposure to pesticides and perhaps also a genetic predisposition. 

So far, CKDu has not been found to be widespread among agricultural workers in the United States. But researchers like Roxana Chicas, an assistant professor of nursing at Emory University, are on the lookout for it. She began researching the effects of heat on agricultural workers when she became a doctoral student at Emory in 2016, and works with Linda McCauley, dean of the nursing school, who has ongoing studies in Florida exploring the effects of heat on immigrant agricultural workers during the summer months. 

Their work found that during just one 10-hour work day where the heat index averaged 89 degrees Fahrenheit, workers’ creatinine levels—a measure of how well their kidneys are functioning—rose to a level consistent with acute kidney injury, and that four out of five of the workers experienced body temperatures that exceeded OSHA’s recommended limit of 100.4 degrees F. Climate change is increasingly producing extreme heat around the country, and farmworkers are particularly vulnerable. This interview with Chicas, conducted over the phone on June 6, has been edited for clarity. 

Do you think that, as climate change worsens, farmworkers in the U.S. will start to develop CKDu?

We do think it could be a potential problem in the future because of the acute kidney injury that we’re seeing now in workers here. That was an unexpected finding. When we started doing our studies in Florida, we were just trying to see if their core body temperatures went over the threshold of 100.4 degrees, which they did and which means they’re essentially working with a fever even though they don’t have an infection. But the acute kidney injury finding, which happened over the course of just one work day, was a surprise.

What kinds of cooling interventions have you tested in your research?

We did a small pilot study, where we randomized workers to either using a cooling bandana or a cooling vest. And then we had a third group that wore both, and a control group. What we found was that the cooling bandana worked well at keeping the workers’ core body temperatures below 100.4 degrees. So it was protective—not statistically significant because it was a small sample of about 80 workers—but very much encouraging. 

Can you describe how the bandana and the vest work?

The inside of the bandana has terry cloth. You wet it, wring it out and put it around your neck. It has direct contact with your large blood vessels on your neck. Workers wear the cooling vests on top of their clothing, so there’s a layer or two of clothing in between it and their skin. I think the general public thinks of agricultural workers as being lean because they work so hard and for so long; in fact, many of them are not. In our studies, about 60 percent of them were overweight, or considered obese based on their body mass index. And so extra adipose tissue made it more difficult for them to get cooled down by the cooling vest. Also the cooling vest weighed about five pounds.

How did the workers try to keep cool before your study?

They used plain bandanas to wipe sweat off their faces. They generally have water in coolers. They are not allowed to have water in the field. They usually have water at the end of a field. However, the further they work in the field, the further the water is. 

Tell me a little bit about who the workers are.

The majority are from Mexico. But there are also many from El Salvador, Guatemala, Honduras, and a few from Cuba and Haiti. So predominantly foreign born. We don’t ask our workers about their immigration status, but we can estimate. For example, we asked workers if they were eligible for funding from the Covid stimulus bill, and about 70 percent of them said that they were not eligible. So we know that probably is because they’re undocumented. They speak Spanish and have limited English proficiency. Many of the workers in Florida are settled workers, they don’t travel around the U.S. for work. They live in multi-family households and some are paid by the piece and they pick ferns for supermarket bouquets or crops such as tomatoes or okra; some work in greenhouses and get paid by the hour.

Roxana Chicas

Tell me about the potential biomarkers you’ve identified that could help determine which workers are more susceptible to heat and acute kidney injury.

We’re still analyzing those biomarkers. We’re also working on a stretchable, breathable sensor —it looks kind of like a Band-Aid—that workers can wear on their chests to measure heart rate and rhythm, skin temperature and other stress indicators. The idea is that the sensor could pick up when a worker’s health starts to decline from heat so that hopefully employers or supervisors would give the workers some relief before they develop more severe symptoms of heat stress. Last summer, we field-tested it on about 20 workers. 

So far, though, employers have not been willing to partner with you for the study?

The growers are not aware that we are conducting these studies and we have not had any luck establishing a relationship with a grower that is willing to collaborate with us. That is why our community partner is the Farmworker Association of Florida. The workers wear the bio-monitoring equipment underneath their clothes. Obviously, the bandana and vest were visible. None of the workers reported being asked about them. 

You were born in El Salvador and were formerly undocumented. Does that help you develop rapport with the workers?

I was undocumented until I was 18. So I share that with them. And I think they like it when they can speak to someone in Spanish and not have to go through an interpreter. Also, some of these workers bring their kids into the office when we’re taking blood samples and the children like to see a nurse that’s Hispanic that speaks Spanish. I certainly didn’t know that I could be a nurse when I was their age. I was 28 when a mentor told me that I could be a nurse, and it just blew my mind. And so, you know, representation matters. And having someone who understands you is really heart-warming for lots of people.